The world's most powerful virtual telescope

Astronomers have successfully combined three telescopes located on Mauna Kea in Hawaii to create the largest virtual telescope for short wavelengths. The Extended SubMillimeter Array (eSMA) connects the signals from the SubMillimeter Array (SMA), consisting of eight dishes with 6-meter diameter, with those from the 15-meter James Clerk Maxwell Telescope (JCMT) and the 10-meter Caltech Submillimeter Observatory (CSO) through fiber-optic cables. The signals from all ten dishes are electronically combined in a large special-purpose computer to create a virtual telescope with a diameter of 782 metres, allowing for an exceptionally sharp view. Preliminary results obtained with this virtual telescope are very promising. They might prefigure what we'll see when the Atacama Large Millimeter Array (ALMA) becomes operational in Chile in 2013. Read more...

Astronomers have successfully combined three telescopes located on Mauna Kea in Hawaii to create the largest virtual telescope for short wavelengths. The Extended SubMillimeter Array (eSMA) connects the signals from the SubMillimeter Array (SMA), consisting of eight dishes with 6-meter diameter, with those from the 15-meter James Clerk Maxwell Telescope (JCMT) and the 10-meter Caltech Submillimeter Observatory (CSO) through fiber-optic cables. The signals from all ten dishes are electronically combined in a large special-purpose computer to create a virtual telescope with a diameter of 782 meters, allowing for an exceptionally sharp view. Preliminary results obtained with this virtual telescope are very promising. They might prefigure what we'll see when the Atacama Large Millimeter Array (ALMA) becomes operational in Chile in 2013. Read more...

Location of the eSMA virtual telescope

You can see above a "satellite view of the eSMA, consisting of the SMA (8 small telescopes above the center), the JCMT (under the right tripod-leg), and the CSO (to the right). The grey overlay illustrates the size of the 'virtual' telescope created by the eSMA through the combination of the three existing facilities." (Credits: satellite image: Google map; montage: Remo Tilanus, JAC) a much larger version which I have reframed for clarity.

If you're not an astronomer, you certainly are wondering why this telescope is using submillimeter techniques. Here is the answer from Netherlands Organisation for Scientific Research (NWO) picked from the page mentioned into the introduction. "The submillimetre wavelength, also known as far-infrared, is light that is invisible to the human eye. It can penetrate dense clouds of interstellar dust and gas, which allows the telescope a clear view of the formation of new stars and planets. The eSMA is a unique device based on interferometry. [...] Interferometry is a technique that has been used in radio astronomy for years, but its application at shorter wavelengths is considerably more difficult. The Dutch astronomer Remo Tilanus of the JCMT can endorse this: 'The three observatories have had to work together closely to get this project off the ground and it's just fantastic that we are now seeing the first astronomical results.' That the new facility can be found at the 4200-metre high summit of Mauna Kea is no coincidence: water vapour in the atmosphere blocks submillimetre radiation so these wavelengths can only be measured in locations with a low humidity and high altitude."

The eSMA is managed by the Joint Astronomy Centre (JAC), an establishment of the UK Science and Technology Facilities Council operated in partnership with Canada and The Netherlands. You'll find additional details on the eSMA and on this project page, "Submillimetre Eagle Eyes on Mauna Kea."

Now, let's look at some the first results obtained by using the eSMA. "One of the first observations of the eSMA, led by Sandrine Bottinelli from Leiden Observatory, targetted a bright radio source seen through the disk of a foreground spiral galaxy. The spiral galaxy acts as a lens and magnifies and splits the light from the background source in two close images. With its sharp view, the eSMA was able to separate these two images and detect the presence of atomic carbon in the disk of the foreground spiral galaxy where it absorbed the light at a very specific frequency towards the southern image. The background radio source is located so far away that the radiation we detect from it left when the universe was only 20% of its current age. Although seen in front of the background radio source, the spiral galaxy itself is also at a large distance and the observations of the carbon in its disc tell us about the physical conditions of interstellar gas at the time the universe was only 45% of its current age."

Here is another example. "In a second result obtained by Hiroko Shinnaga (CSO), the eSMA zoomed in on the envelope of a nearby star, called IRC+10216 or CW Leo. This star is in an evolved stage and is close to the end of its life. During this phase a star expels a lot of the gas in its outer layers to form an envelope and, by tracing the hydrogen cyanide molecule (HCN), the eSMA observed for the first time in detail the zone where molecules form from the gas and are being accelerated away."

For more information, you can follow the numerous links provided by the eSMA page mentioned above. You might also read two not too technical articles, "Telescopes unite to sharpen their focus" (AP, November 17, 2008) and "Submillimetre Eagle Eyes On Mauna Kea" (Space Daily, November 14, 2008).

Sources: Netherlands Organisation for Scientific Research (NWO), November 10, 2008; and various websites

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